The Intel Core i5-661 processor represents the next generation of mid-range processors that will power many of the new desktop PCs released this year. It runs at 3.33GHz and has two physical cores with Hyper-Threading. More importantly, it's one of Intel's first 32 nanometre (nm) CPUs and one of the first to feature a built-in Intel GMA HD graphics processor, and was codenamed "Clarkdale".
The main differences between the Core i5-661 and the Core i5-750 (the first Core i5 CPU, released in September 2009) are the 32nm manufacturing process for the CPU and the 45nm process for integrated HD graphics. Along with the graphics chip, the Core i5-661 also has a built-in DDR3 memory controller and a PCI Express controller, so it's a little beast of a chip that takes a lot of the responsibility away from the motherboard itself. It also has 4MB of Level 3 cache, extensive power management features that kick in when the CPU is idle, as well as Turbo Boost, which can run the CPU at a faster-than-rated rate.
It's the 32nm manufacturing process that has allowed Intel to include so many components and transistors in a single physical chip. You won't be able to just upgrade your current PC by swapping in the latest processor. For example, if you're the owner of an Intel P55 chipset-based motherboard, the Core i5-661 will run but its graphics chip won't be usable. It requires a new motherboard with one of Intel's latest H55 or H57 chipsets in order to make the integrated graphics work. Similarly, the graphics ports on a motherboard designed for the Core i5-661 (or any of the other Core i5-600 series processors) won't work unless you use an Intel Core i5 600-series processor with integrated graphics.
For our tests, we used an Intel DH55TC desktop motherboard which offers the LGA1156 CPU socket. The Intel H55 Express chipset is used to control the Serial ATA ports, Gigabit Ethernet port, USB 2.0 ports, digital audio, graphics ports and PCI Express expansion slots. It's the only major chip on the motherboard, but that doesn't mean that vendors can automatically just shrink the size of the circuit board and make smaller PCs — the DH55TC is a micro-ATX board, which is as small as it gets for a mainstream board — but it means that the board itself will produce less heat. This is because there isn't a separate graphics chip on the motherboard anymore, the graphics is part of the processor itself and benefits from the heatsink and active cooling fan that is mounted on top of it.
While systems based on the new CPU can run cooler, they will also run very swiftly. Turbo Boost is a technology that Intel introduced with the first Core i5-750 CPU, and it works by automatically allowing the CPU to run faster depending on the number of cores that are in use. On a dual-core CPU such as the Core i5-661, Turbo Boost can be used to its maximum potential — while the CPU is rated at 3.33GHz, it often runs at 3.6GHz when TurboBoost is active. Coupled with 4MB of Level 3 cache and Hyper-Threading, which allows up to four instructions to be processed by the CPU at one time (effectively making it a quad-core CPU), the Core i5-661 can be very fast. However, Turbo Boost increases the raw MegaHertz available to applications, at the cost of halving the number of processor cores used - thus running only 2 threads simultaneously as opposed to the four threads available otherwise on a dual-core processor with HyperThreading support.
In our iTunes MP3 test, where we encode 53 minutes worth of WAV files to 192Kbps MP3 files, the CPU only took 45sec, which is about 7sec faster than a 2.66GHz Core i5-750 CPU. The Core i5-661 performed better during this test because it's 670MHz faster than the quad-core Core i5-750 and iTunes only uses two cores. However, even in an application that can handle four cores, such as Blender 3D, the Core i5-661 held its own. When running four cores (two real ones and two virtual ones thanks to Hyper-Threading), the Core i5-661 took 42sec to render a 3D image. This is just about 6sec slower than the Core i5-750 that uses four real CPU cores. It shows that Hyper-Threading can make a significant difference to a dual-core CPU.
In our WorldBench 6 application test suite, the Core i5-661's 3.33GHz clock speed was again a major highlight. It managed to record an overall score of 130, which is faster than any Core i5-750 scores seen. This bodes very well, considering the quad-core i5-750 itself is no slouch with a performance that could out-strip most "high-end" desktops bought just 6 months ago. We conducted our tests using the built-in Intel HD graphics, 2GB of Kingston DDR3 HyperX 2000MHz RAM, and an Intel SSD (X25-M 80GB). After adding a relatively modest graphics card to the mix (GeForce 9600GT), the score improved to 139.
The 7% decrease in performance when using the integrated graphics won't be noticeable during everyday usage, and the CPU with its built-in graphics enabled is still fast enough to be used in a media center PC — it will be capable of decoding high definition TV channels, for example. Eliminating the need for a separate graphics card also means that a media center running this CPU can be cooler and run much more quietly. How much cooler? We decided to run the 661 at full load for half-an-hour and then checked the CPU temperature reported by Everest - all of 45 degrees Celsius! To understand its significance, note that the quad-core Core i7 870 runs atleast 10 degrees Celsius hotter under full load - all of this having been tested in an open-rig environment, so temperatures within a desktop cabinet can be expected to get even warmer, considering warm summers seen in India.
If you're a gamer, the integrated graphics won't be much of a boon to you even though it supports OpenGL 2.1 and DirectX 10 with a 2560x1600 display output resolution. You'll still need a separate graphics card to play any games that require serious 3D processing. For example, in 3DMark06 the CPU with integrated graphics enabled achieved a score of 2525. This score is actually not bad at all for an integrated graphics solution, and it may run some old games adequately. However, it doesn't crunch frames fast enough to allow you to play many of the latest 3D titles smoothly. When we added an NVIDIA GeForce 9600GT-based graphics card, the 3DMark06 score improved to 11,855 points. To sum up the relative position of the integrated graphics, the scores seen on the i5-661 are better than all previous Intel integrated graphic solutions. It is also better than desktop motherboards with integrated graphics from nVidia and AMD, except for the AMD 785G chipset which gives neck-and-neck competition.
The best application of the Core i5-661 CPU is in a budget PC, small media centre PC or a silent PC where 3D graphics aren't a huge priority. A smaller-than-usual heat sink and fan assembly ships with the Core i5-661, and it makes barely any noise at all when it's running. You'd be hard-pressed to hear it in a typical room. The Core i5-661 is priced around Rs. 13,500, which is actually cheaper than a C2D E8600 3.3GHz processor priced at Rs. 14,500. Motherboards based on the H55 chipset can be bought for about Rs. 6,500, so for about Rs. 20k you get the basic building blocks for a very potent and versatile new PC.
You can see images of the above-mentioned processor, cooler and motherboard to the left of this review. For more details of the performance scores seen during testing, click the "Performance" tab of this review. Note that the Core i5-661 processor has a graphics core clocked at a higher speed (900 MHz) than the others in the i5-600 series (733 MHz). To read PC World's preview with details of the newly launched dual-core 32nm processors with integrated graphics, and see how the graphics compare against mother-board integrated graphics solutions, click here.
With the Core i5-661, Intel has released a CPU that can just about do it all: it's a CPU, graphics controller, memory controller and PCI Express controller in one. It performed well in our tests, the integrated graphics and reasonably cool temperatures make it a good choice for a media center. The only downside is that you have to fork over cash for a motherboard as well, but that's standard for any major upgrade.